Microphthalmia

Microphthalmia
Specialty	Medical genetics

Microphthalmia (or microphthalmos) is a congenital deformation resulting in abnormally small eyes. It may involve one or both eyes.

Presentation

In mammals the failure of expression of the transcription factor, MITF (microphthalmia-associated transcription factor), in the pigmented retina prevents this structure from fully differentiating. This in turn causes a malformation of the choroid fissure of the eye, resulting in the drainage of vitreous humor fluid. Without this fluid, the eye fails to enlarge, thus the name microphthalmia.

Causes

The gene encoding the microphthalmia-associated transcription factor (MITF) is a member of the basic helix-loop-helix-leucine zipper (bHLH-ZIP) family. Waardenburg syndrome type 2 (WS type 2) in humans is also a type of microphthalmia syndrome. Mutations in MITF gene are thought to be responsible for this syndrome. The human MITF gene is homologous to the mouse MITF gene (aka mouse mi or microphthalmia gene); mouse with mutations in this gene are hypopigmented in their fur. The identification of the genetics of WS type 2 owes a lot to observations of phenotypes of MITF mutant mice.

Microphthalmia in newborns is also associated with infections during pregnancy, particularly rubella and cytomegalovirus (CMV), trisomy 13 (Patau syndrome), Triploid Syndrome, and Wolf-Hirschhorn Syndrome. In addition, microphthalmia may also be a result of fetal alcohol syndrome.

External links

• Parent Support group for parents with Anophthalmic and Microphthalmic children MAPS
• Anophthalmia and Microphthalmia Resource Guide from the National Eye Institute (NEI).
• GeneReview/NIH/UW entry on Lenz Microphthalmia Syndrome associated with BCOR (MAA2 locus) gene mutaions
• Stories of eye loss Personal stories about kids and eye loss
• MACS The Micro and Anophthalmic Childrens Society - Offers support and Information to families in the UK and around the world